Synthesis and Characterization of a Novel Cyanate Ester Containing Dimethyl Benzene Linkage

Renewable phenols derived from biomass sources often contain methoxy groups that alter the properties of derivative polymers. To evaluate the impact of o-methoxy groups on the performance characteristics of cyanate ester resins, three bisphenols derived from the renewable phenol creosol were deoxygenated by conversion to ditriflates followed by palladium-catalyzed elimination and hydrolysis of the methoxy groups. The deoxygenated bisphenols were then converted to the following cyanate ester resins: bis(4-cyanato-2-methylphenyl)methane (16), 4,4′-(ethane-1,1′-diyl)bis(1-cyanato-3-methylbenzene) (17), and 4,4′-(propane-1,1′-diyl)bis-(1-cyanato-3-methylbenzene) (18). The physical properties, cure chemistry, and thermal stability of these resins were evaluated and compared to those of cyanate esters derived from the oxygenated bisphenols. 16 and 18 had melting points 37 and >95°C lower, respectively, than the oxygenated versions, while 17 had a melting point 14°C higher. The T g 's of thermosets generated from the deoxygenated resins ranged from 267 to 283°C, up to 30°C higher than the oxygenated resins, while the onset of thermal degradation was 50−80°C higher. The deoxygenated resins also exhibited water uptakes up to 43% lower and wet T g s up to 37°C higher than the oxygenated resins. TGA-FTIR of thermoset networks derived from 16−18 revealed a different decomposition mechanism compared to the oxygenated resins. Instead of a low-temperature pathway that resulted in the evolution of phenolic compounds, 16−18 had significantly higher char yields and decomposed via evolution of small molecules including isocyanic acid, CH 4 , CO 2 , and NH 3 .

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Effects of o-Methoxy Groups on the Properties and Thermal Stability of Renewable High-Temperature Cyanate Ester Resins

Harvey

Guenthner

Lai

et al. 2015

Macromolecules

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Synergistic Physical Properties of Cocured Networks Formed from Di- and Tricyanate Esters

Guenthner

Reams²,

Lamison³

et al. 2013

ACS Appl. Mater. Interfaces

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The co-cyclotrimerization of two tricyanate ester monomers, Primaset PT-30 and 1,2,3-tris(4-cyanato)propane (FlexCy) in equal parts by weight with Primaset LECy, a liquid dicyanate ester, was investigated for the purpose of exploring synergistic performance benefits. The monomer mixtures formed stable, homogeneous blends that remained in the supercooled liquid state for long periods at room temperature, thereby providing many of the processing advantages of LECy in combination with significantly higher glass transition temperatures (315-360 °C at full cure) due to the presence of the tricyanate-derived segments in the conetwork. Interestingly, the glass transition temperatures of the conetworks after cure at 210 °C, at full cure, and after immersion in 85 °C water for 96 h were all higher than predicted by the Flory-Fox equation, most significantly for the samples immersed in hot water. Conetworks comprising equal parts by weight of PT-30 and LECy retained a "wet" glass transition temperature near 270 °C. The onset of thermochemical degradation for conetworks was dominated by that of the thermally less stable component, while char yields after the initial degradation step were close to values predicted by a linear rule of mixtures. Values for moisture uptake and density in the conetworks also showed behavior that was not clearly different from a linear rule of mixtures. An analysis of the flexural properties of catalyzed versions of these conetworks revealed that, when cured under the same conditions, conetworks containing 50 wt % PT-30 and 50 wt % LECy exhibited higher modulus than networks containing only LECy while conetworks containing 50 wt % FlexCy and 50 wt % LECy exhibited a lower modulus but significantly higher flexural strength and strain to failure. Thus, in the case of "FlexCy", LECy was copolymerized with a tricyanate that provided both improved toughness and a higher glass transition temperature.

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Cyanate Ester Monomers and Oligomers. Overview of the Modern Research State and Perspectives

Anshin¹

2022

Polym. Sci. Ser. B

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Synthesis and Characterization of a Novel Cyanate Ester Containing Dimethyl Benzene Linkage

Cited by 3 publications

References 14 publications

Effects of o-Methoxy Groups on the Properties and Thermal Stability of Renewable High-Temperature Cyanate Ester Resins

Effects of o-Methoxy Groups on the Properties and Thermal Stability of Renewable High-Temperature Cyanate Ester Resins

Synergistic Physical Properties of Cocured Networks Formed from Di- and Tricyanate Esters

Cyanate Ester Monomers and Oligomers. Overview of the Modern Research State and Perspectives

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